Active suspension device and control device for suspension

ABSTRACT

An ECU includes: a road surface height measurer which measures road surface heights at three or more points along a vehicle-width direction in front of a tire mounted on a wheel; a position detector which detects a position at which a difference of the road surface height from an adjacent road surface height is equal to or larger than a predetermined threshold among the road surface heights at three or more points measured by the road surface height measurer; and a corrector which corrects the road surface height at a position at which the difference detected by the position detector is equal to or larger than the predetermined threshold to a predetermined height.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an active suspension device and acontrol device for suspension.

2. Description of the Related Art

Patent Literature 1 discloses “a control device for active suspensionwhich detects, and stores in time-series, a displacement X of a roadsurface and a vertical acceleration G at a front end of a vehicle body,and which estimates a displacement of the road surface when a vehiclepasses therethrough from the displacement X, and controls actuators offront wheels and rear wheels depending on the estimated displacement ofthe road surface when detection of the displacement is normal, and whichestimates a vertical acceleration of a part of the vehicle bodycorresponding to the rear wheels from the vertical acceleration G basedon a wheel base Lw and a vehicle speed, and controls the actuator of therear wheels depending on the estimated vertical acceleration when thedetection of the displacement is abnormal” (see for example the abstractof Patent Literature 1).

-   Patent Literature 1: JP H05-096922 A

In the control device for active suspension disclosed in PatentLiterature 1, a controller determines whether or not the detection ofdisplacement by a road surface detector is normal, and when it isdetermined that the detection of displacement is normal, the controllerestimates the displacement of the road surface when the vehicle travelsfor a predicted distance from the displacement of the road surfacestored in a storage based on at least the predicted distance and thevehicle speed, and controls the actuators depending on the estimateddisplacement of the road surface.

On the other hand, when it is determined that the detection of thedisplacement is abnormal, the controller estimates the verticalacceleration of a part of the vehicle body corresponding to the rearwheels when the vehicle travels for a distance of the wheel base fromthe vertical acceleration stored in the storage based on the wheel baseand the vehicle speed, and controls the actuator of the rear wheelsdepending on the estimated vertical acceleration.

As described above, since when it is determined that the detection ofthe displacement is abnormal, the actuator of the rear wheels iscontrolled depending on the vertical acceleration estimated from thevertical acceleration stored in the storage, there is a risk that theride comfort of an occupant of the car deteriorates.

SUMMARY OF THE INVENTION

The present invention solves the above-described conventional problem,and has an object to provide an active suspension device and a controldevice for suspension which are capable of preventing a ride comfort ofan occupant of a car from deteriorating.

An active suspension device according to the present invention is acontrol device for a variable damping force damper provided for dampinga relative vibration between a vehicle body and a wheel, including: aroad surface height measurer which measures road surface heights atthree or more points along a vehicle-width direction in front of a tiremounted on the wheel; a position detector which detects a position atwhich a difference of the road surface height from an adjacent roadsurface height is equal to or larger than a predetermined thresholdamong the road surface heights at three or more points measured by theroad surface height measurer; and a corrector which corrects the roadsurface height at a position at which the difference detected by theposition detector is equal to or larger than the predetermined thresholdto a predetermined height.

According to the present invention, it is possible to provide an activesuspension device and a control device for suspension which are capableof preventing a ride comfort of an occupant of a car from deteriorating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic configuration view of a vehicle to which asuspension control device according to an embodiment of the presentinvention is applied;

FIG. 2 is a side view of the vehicle showing an attachment structure ofa sensor in the present embodiment;

FIG. 3 is a functional block diagram showing functions of an ECUaccording to the present embodiment;

FIG. 4A is an explanatory diagram showing a measurement result in whicha position detector measured road surface heights along a vehicle-widthdirection in front of a tire;

FIG. 4B is an explanatory diagram showing a concept in which a correctorcorrects to a limit value up to which the tire is deformable;

FIG. 5A is an explanatory diagram showing a measurement result ofmeasuring road surface heights at a certain time;

FIG. 5B is an explanatory diagram showing a measurement result ofmeasuring road surface heights at a different time (No. 1);

FIG. 5C is an explanatory diagram showing a measurement result ofmeasuring road surface heights at a different time (No. 2);

FIG. 5D is an explanatory diagram showing a measurement result ofmeasuring road surface heights at a different time (No. 3);

FIG. 6A is an explanatory diagram showing that a difference of a valueof a road surface height at one point from road surface heights atadjacent measurement points is larger than a first threshold; and

FIG. 6B is an explanatory diagram showing that each of differences ofvalues of road surface heights at two points respectively from roadsurface heights at adjacent measurement points is equal to or largerthan a predetermined threshold.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail. Note that the embodiments described below are examples forimplementing the present invention and should be modified or changed asappropriate depending on the configurations of devices to which thepresent invention is applied and on various conditions, and the presentinvention is not limited to the following embodiments. In addition,parts of the embodiments described below may be combined as appropriate.

FIG. 1 shows a schematic configuration view of a vehicle V to which asuspension control device according to an embodiment of the presentinvention is applied. FIG. 2 is a side view of the vehicle V showing anattachment structure of a sensor 3 in the present embodiment. Note thatthe contour of the vehicle V is indicated by dashed-two dotted lines inFIG. 2 .

As shown in FIG. 1 or FIG. 2 , the vehicle (car) V includes avehicle-body member 1, an exterior member 2, sensors 3, and an ECU(Electronic Control Unit) 4. The model or type of the vehicle V is notparticularly limited as long as the vehicle V is a car including thevehicle-body member 1, the exterior member 2, the sensors 3, and the ECU4. In other words, the vehicle V is a passenger vehicle, a bus, a truck,a service vehicle, or the like.

In the vehicle-body member 1 of the vehicle V, wheels 16 equipped withtires 15 are arranged as front wheels. Each wheel 16 of the front wheelsis suspended on the exterior member 2 by means of a suspension composedof a suspension arm 18, a spring 20, a variable damping force damper(hereinafter simply referred to as the damper D), and the like. Notethat the present embodiment will be described with an electromagneticdamper as an example, but is not limited to this, and may be applied toan air suspension and an active suspension using an active stabilizer.In addition, although the present embodiment will be described with thefront wheel as an example, the same configuration as the wheel 16 of thefront wheel may be employed for the wheels of the rear wheels.

As shown in FIG. 2 , the vehicle-body member 1 supports the exteriormember 2 and includes front side frames 11, upper members 12, bumperbeam extensions 13, a bumper beam 14 (frame member), and the like.

The exterior member 2 is a member that forms the exterior part (exteriorshell) of the vehicle V. The exterior member 2 includes an engine hood21, a front bumper 22 (bumper), and front fenders 23. The engine hood 21is a panel member that covers the upper face in front of the windshield.The front bumper 22 is located on the front face side of the vehicle Vand is composed of a panel member made of a synthetic resin, forexample. In addition, the front bumper 22 includes a front face portion22 a, which is provided with an air intake and the like, and a bottomface portion 22 b, which extends rearward from the lower end of thefront face portion 22 a. The front fenders 23 are panel members thatcover the surroundings of the wheels 16.

As shown in FIG. 1 and FIG. 2 , the sensor 3 is a sensor for dampercontrol that detects the condition of the road surface R (road surfacecondition) in front of the vehicle V to control the damper D of thevehicle V. The sensor 3 acquires information on the heights of the roadsurface at three or more points. The sensor 3 is fixed to the uppermember 12 (see FIG. 2 ) which is located in front of the wheel 16. Thesensor 3 in the present embodiment is configured to detect the conditionof the road surface R immediately ahead of the wheel 16 as indicated bythe solid-line arrow in FIG. 2 , and may be selected as appropriate fromsensors of radar system, camera system, laser system, and the like. Inaddition, the sensor 3 is not limited to a single sensor, but may beconfigured by combining sensors of multiple systems, like a camerasystem and a laser system.

The ECU 4 (active suspension device) shown in FIG. 1 is a device thatcontrols the damper D, which is provided for damping a relativevibration between the vehicle-body member 1 and the wheel 16. In thepresent embodiment, a road surface condition detector is composed of thesensor 3 and the ECU 4.

The ECU 4 is composed of a microcomputer, a ROM, a RAM, a peripheralcircuit, an input-output interface, various drivers, and the like. TheECU 4 is electrically coupled to each sensor 3 and the damper D of eachwheel 16 through a communication line (for example, a controller areanetwork (CAN): not shown). In addition, a suspension control device(control device for suspension) is composed of the ECU 4 and the sensor3. In other words, the suspension control device is configured tocontrol suspension including the damper D, where the road surfacecondition detector is composed of the sensor 3 and the ECU 4.

In the present embodiment, the damper D is composed of, for example, amonotube-type (de Carbon-type) damper. In this damper D, a piston rod ishoused in a tubular cylinder filled with a magneto-rheological fluid(MRF) such that the piston rod is slidable in an axial direction, and apiston mounted on the front end of the piston rod partitions the insideof the cylinder into an upper fluid chamber and a lower fluid chamber.Between the upper fluid chamber and the lower fluid chamber, acommunication passage through which the upper fluid chamber and thelower fluid chamber communicate with each other is provided. Inside thecommunication passage, an MLV coil is disposed. In the damper D, forexample, the lower end of the cylinder is coupled to the suspension arm18, which is a wheel-side member, and the upper end of the piston rod iscoupled to a damper base, which is a vehicle body-side member.

In addition, once a current is supplied to the MLV coil, which is notshown, of the damper D by the ECU 4, a magnetic field is applied to theMRF flowing through the communication passage, and a chain cluster offerromagnetic particles is formed. This increases the apparent viscosityof the MRF passing through the communication passage to increase thedamping force of the damper D. Note that although a monotube-type damperis employed as the damper D in the present embodiment, dampers of othertypes may be employed as appropriate.

FIG. 3 is a functional block diagram showing functions of the ECU 4according to the present embodiment. The ECU 4 functions as a roadsurface height measurer 41, a position detector 42, a corrector 43, anda road surface condition determiner 44 by executing programs stored inthe not-shown ROM.

The road surface height measurer 41 measures road surface heights atthree or more points along a vehicle-width direction in front of thetire 15 mounted on the wheel 16. For example, the sensor 3 acquiresinformation on the road surface heights at three or more points. Thesensor 3 acquires reflected light of laser from the road surface R todetect the condition of the road surface R (road surface condition) infront of the vehicle V. In this way, the road surface height measurer 41acquires the road surface condition from the sensor 3 and measures theroad surface heights at three or more points along the vehicle-widthdirection in front of the tire 15 mounted on the wheel 16.

The position detector 42 detects a position at which a difference of theroad surface height from an adjacent road surface height is equal to orlarger than a predetermined threshold among the road surface heights atthree or more points measured by the road surface height measurer 41.

FIG. 4A is an explanatory diagram showing a measurement result in whichthe position detector 42 measured road surface heights along thevehicle-width direction in front of the tire 15.

As shown in FIG. 4A, the horizontal axis indicates the width directionof the tire 15, and the vertical axis indicates the road surface heightin front of the tire 15. That is, FIG. 4A shows road surface heights HT1to HT5 at measurement points MP1 to MP5 in front of the tire 15.

The corrector 43 corrects a road surface height at a position at whichthe difference detected by the position detector 42 is equal to orlarger than the predetermined threshold TL to a predetermined height.For example, the corrector 43 corrects the road surface heights HT3, HT4at positions at which the difference detected by the position detector42 is equal to or larger than the predetermined threshold TL topredetermined heights CP1, CP2.

Specifically, the corrector 43 corrects the road surface heights HT3,HT4 the differences of which from the road surface height HT2 of themeasurement point MP2 are equal to or larger than the predeterminedthreshold TL to limit values known in advance up to which the tire 15 isdeformable (hereinafter referred to as deformation limits). Note thatthe configuration in which the corrector 43 corrects road surfaceheights to limit values up to which the tire 15 is deformable is anexample of the present embodiment, and the present embodiment is notlimited to this.

FIG. 4B is an explanatory diagram (tire deformation model) showing theconcept in which the corrector 43 corrects road surface heights to thelimit values up to which the tire 15 is deformable. The tire deformationmodel shown in FIG. 4B indicates that when a measured road surfaceheight exceeds the deformation limit of the tire 15 on the road surfaceR, the corrector 43 corrects the measured road surface height to thedeformation limit of the tire 15.

For example, in FIG. 4A, when differences between the road surfaceheight HT2 at the measurement point MP2 and the road surface heightsHT3, HT4 at the measurement points MP3, MP4 exceed the predeterminedthreshold TL, the corrector 43 corrects the road surface height HT3 atthe measurement point MP3 to the predetermined height CP1 (thedeformation limit of the tire deformation model) which indicates a limitvalue up to which the tire 15 is deformable, and also corrects the roadsurface height HT4 at the measurement point MP4 to the predeterminedheight CP2 (the deformation limit of the tire deformation model) whichindicates a limit value up to which the tire 15 is deformable.

On the other hand, the road surface condition determiner 44 (see FIG. 3) excludes a value of the road surface height at a position at which thedifference detected by the position detector 42 is equal to or largerthan the predetermined threshold TL, and determines a condition of theroad surface based on the road surface heights at positions at each ofwhich the difference from an adjacent road surface height is smallerthan the predetermined threshold. Note that the corrector 43 and theroad surface condition determiner 44 may be combined with each other tobe used as optional constituent elements.

In the case where the ECU 4 includes the road surface conditiondeterminer 44, the corrector 43 corrects the excluded value of the roadsurface height at a position at which the difference is equal to orlarger than the predetermined threshold TL based on the road surfaceheights at positions at each of which the difference from an adjacentroad surface heights is smaller than the predetermined threshold TL.Here, examples in which the corrector 43 performs correction will bedescribed using FIG. 5A to FIG. 5D.

FIG. 5A is an explanatory diagram showing a measurement result (roadsurface heights HT1 to HT5) of measuring road surface heights at acertain time. FIG. 5A shows that there is no measurement point at whichthe difference of the road surface height from an adjacent road surfaceheight is equal to or larger than a predetermined threshold inmeasurement points MP1 to MP5, for example.

In this case, in the present embodiment, the ECU 4 uses the road surfaceheights HT1 to HT5 at the respective measurement points MP1 to MP5 inFIG. 5A as values for controlling the damper D.

FIG. 5B is an explanatory diagram showing a measurement result (roadsurface heights HU1 to HU5) of measuring road surface heights at adifferent time. As shown in FIG. 5B, in the measurement points MP1 toMP5, for example, the difference of the road surface height HU2 at themeasurement point MP2 from the adjacent road surface height HU1 (or theroad surface height HU3) is equal to or larger than a first thresholdTL1 (predetermined threshold). In this case, the road surface conditiondeterminer 44 excludes the value of the road surface height HU2 at themeasurement point MP2, and determines the condition of the road surfacebased on the road surface heights HU1, HU3, HU4, HU5 at the positions ateach of which the difference from the adjacent road surface height issmaller than the first threshold TL1.

Hence, the corrector 43 corrects the excluded value of the road surfaceheight HU2 at the measurement point MP2 at which the difference is equalto or larger than the first threshold TL1 based on the road surfaceheights HU1, HU3, HU4, HU5 at positions at each of which the differencefrom the adjacent road surface height is smaller than the firstthreshold TL1. That is, the corrector 43 corrects the value of the roadsurface height HU2 at the measurement point MP2 such that the differencefrom the road surface height HU1 (the adjacent road surface height)becomes smaller than the first threshold TL1.

In this way, in the present embodiment, the ECU 4 uses the road surfaceheights HU1, HU3, HU4, HU5 in FIG. 5B and the corrected value of theroad surface height HU2 at the measurement point MP2 as values forcontrolling the damper D.

FIG. 5C is an explanatory diagram showing a measurement result (roadsurface heights HV1 to HV5) of measuring road surface heights at adifferent time. As shown in FIG. 5C, in the measurement points MP1 toMP5, for example, the difference of the road surface height HV3 at themeasurement point MP3 from the adjacent road surface height HV2 (or theroad surface height HV4) is equal to or larger than the first thresholdTL1. In this case, the road surface condition determiner 44 excludes thevalue of the road surface height HV3 at the measurement point MP3, anddetermines the condition of the road surface based on the road surfaceheights HV1, HV2, HV4, HV5 at the positions at each of which thedifference from the adjacent road surface height is smaller than thefirst threshold TL1.

Hence, the corrector 43 corrects the excluded value of the road surfaceheight HV3 at the measurement point MP3 at which the difference is equalto or larger than the first threshold TL1 based on the road surfaceheights HV1, HV2, HV4, HV5 at positions at each of which the differencefrom the adjacent road surface height is smaller than the firstthreshold TL1. That is, the corrector 43 corrects the value of the roadsurface height HV3 at the measurement point MP3 such that the differencefrom the road surface height HV2 (the adjacent road surface height)becomes smaller than the first threshold TL1.

In this way, in the present embodiment, the ECU 4 uses the road surfaceheights HV1, HV2, HV4, HV5 in FIG. 5C and the corrected value of theroad surface height HV3 at the measurement point MP3 as values forcontrolling the damper D.

FIG. 5D is an explanatory diagram showing a measurement result (roadsurface heights HW1 to HW5) of measuring road surface heights at adifferent time. As shown in FIG. 5D, in the measurement points MP1 toMP5, for example, the difference of the road surface height HW1 at themeasurement point MP1 from the adjacent road surface height HW2 is equalto or larger than the first threshold TL1. In this case, the roadsurface condition determiner 44 excludes the value of the road surfaceheight HW1 at the measurement point MP1, and determines the condition ofthe road surface based on the road surface heights HW2, HW3, HW4, HW5 atthe positions at each of which the difference from the adjacent roadsurface heights is smaller than the first threshold TL1.

Hence, the corrector 43 corrects the excluded value of the road surfaceheight HW1 at the measurement point MP1 at which the difference is equalto or larger than the first threshold TL1 based on the road surfaceheights HW2, HW3, HW4, HW5 at positions at each of which the differencefrom the adjacent road surface height is smaller than the firstthreshold TL1. That is, the corrector 43 corrects the value of the roadsurface height HW1 at the measurement point MP1 such that the differencefrom the road surface height HW2 (the adjacent road surface height)becomes smaller than the first threshold TL1.

Hence, in the present embodiment, the ECU 4 uses the road surfaceheights HW2, HW3, HW4, HW5 in FIG. 5D and the corrected value of theroad surface height HW1 at the measurement point MP1 as values forcontrolling the damper D.

In this way, in the case where one road surface height is different froman adjacent road surface height by the first threshold TL1 or more, theECU 4 can exclude the value of the one road surface height, anddetermine the condition of the road surface based on the other roadsurface heights at positions at each of which the difference is smallerthan the first threshold TL1. In this case, the measurement points arenot limited regardless of which of the right side and the left side ofthe tire 15 they are on as long as the road surface heights areadjacent.

Moreover, for the case where there is one point at which the differencefrom an adjacent road surface height is equal to or larger than thepredetermined threshold and the case where there are two points at eachof which the difference from an adjacent road surface height is equal toor larger than the predetermined threshold, the position detector 42 maybe such that a second threshold for detecting the differences in roadsurface height at two points is set to be larger than the firstthreshold for detecting difference in road surface height at one point.Here, a relation between the first threshold and the second thresholdwill be described in detail with comparison between these thresholdswith reference to the drawings.

FIG. 6A shows that a difference of the value of the road surface heightHU2 at one point from the adjacent road surface heights HU1, HU3 at themeasurement points MP1, MP3 is larger than the first threshold TL1. Onthe other hand, FIG. 6B shows each of differences of the values of theroad surface heights HT6, HT7 at two points respectively from the roadsurface heights 0, HT3 at the adjacent measurement points 0, MP3 isequal to or larger than a predetermined threshold. Note that parts inFIG. 6A and FIG. 6B which are common with FIG. 5A and FIG. 5B aredenoted by the same reference signs, and the description of such partswill be omitted. In addition, the first threshold TL1 and the secondthreshold TL2 are variable.

In FIG. 6A, since the difference of the road surface height HU2 from theadjacent road surface height HU1 or road surface height HU3 is largerthan the first threshold TL1, the road surface height HU2 is excluded asan outlier point from the road surface heights used for determining thecondition of the road surface.

On the other hand, in FIG. 6B, the position detector 42 detects twopoints of the road surface heights HT6, HT7 as positions at each ofwhich the difference from the adjacent road surface height is equal toor larger than the predetermined threshold. In this case, as shown inFIG. 6B, the position detector 42 sets the second threshold TL2 fordetecting differences in road surface height at two points to be largerthan the first threshold TL1 for detecting a difference in road surfaceheight at one point. This enables the position detector 42 to make theroad surface heights HT6, HT7 at two points less likely to be excludedas outlier points than in the case of the road surface height HT6, HT7at one point.

Here, for example, if the first threshold TL1 and the second thresholdTL2 were the same value, the road surface condition determiner 44 woulddetect the road surface heights HT6, HT7 at adjacent two points shown inFIG. 6B as outlier points, which is unfavorable in consideration of theactual road surface heights.

In view of this, the position detector 42 can make each of the values ofthe road surface heights HT6, HT7 at the adjacent two points less likelyto be detected as an outlier point by making the second threshold TL2for detecting differences in road surface height at two points largerthan the first threshold TL1 for detecting a difference in road surfaceheight at one point.

In this way, the road surface condition determiner 44 can avoidexcluding the road surface heights HT6, HT7 at the adjacent two pointsas outlier points, and accordingly the ECU 4 can improve the accuracy indetermining the condition of the road surface. Note that the relationbetween the second threshold TL2 and the first threshold TL1 only has tobe such that the second threshold TL2 is relatively larger than thefirst threshold TL1, and does not have to be determined based onabsolute values.

First Embodiment

An ECU 4 according to a first embodiment includes: a road surface heightmeasurer 41 which measures road surface heights at three or more pointsalong a vehicle-width direction in front of a tire 15 mounted on a wheel16; a position detector 42 which detects a position at which adifference of the road surface height from an adjacent road surfaceheight is equal to or larger than a predetermined threshold among theroad surface heights at three or more points measured by the roadsurface height measurer 41; and a corrector 43 which corrects the roadsurface height at a position at which the difference detected by theposition detector 42 is equal to or larger than the predeterminedthreshold to a predetermined height.

In this way, the ECU 4 according to the first embodiment measures roadsurface heights at three or more points along the vehicle-widthdirection in front of the tire 15 mounted on the wheel 16, and correctsa road surface height at a position at which the difference from anadjacent road surface height is equal to or larger than thepredetermined threshold among the measured road surface heights at threeor more points to the predetermined height. Hence, since the ECU 4 canappropriately correct road surface heights, it is possible to improve adetection accuracy in detecting the condition of the road surface.

As described above, the ECU 4 according to the first embodiment measuresroad surface heights at three or more points, and corrects a roadsurface height at a position at which the difference from an adjacentroad surface height is equal to or larger than the predeterminedthreshold among the measured road surface heights at three or morepoints to a predetermined height.

Hence, since the ECU 4 according to the first embodiment canappropriately correct road surface heights, it is possible to improve adetection accuracy in detecting the condition of the road surface, andto thus prevent the ride comfort of an occupant in a car fromdeteriorating. Specifically, the ECU 4 can appropriately correct roadsurface heights even when woven wires or stones are stacked on the roadsurface.

In addition, in the first embodiment, the ECU 4 may further include aroad surface condition determiner 44 which excludes a value of the roadsurface height at the position at which the difference detected by theposition detector 42 is equal to or larger than the predeterminedthreshold, and determines the condition of the road surface based on theroad surface heights at positions at each of which the difference froman adjacent road surface height is smaller than the predeterminedthreshold.

In this way, the ECU 4 according to the first embodiment detects aposition at which the difference from an adjacent road surface height isequal to or larger than the predetermined threshold, excludes a value ofthe road surface height at the position at which the detected differenceis equal to or larger than the predetermined threshold, and can thusdetermine the condition of the road surface based on the road surfaceheights at positions at each of which the difference from an adjacentroad surface height is smaller than the predetermined threshold.

In this case, the corrector 43 corrects the excluded value of the roadsurface height at the position at which the difference is equal to orlarger than the predetermined threshold (for example, the firstthreshold) based on the road surface heights at positions at each ofwhich the difference is smaller than the predetermined threshold (forexample, the first threshold).

Moreover, for the case where there is one point at which the differencefrom an adjacent road surface height is equal to or larger than thepredetermined threshold and the case where there are two points at eachof which the difference from an adjacent road surface height is equal toor larger than the predetermined threshold, the position detector 42 maybe such that a second threshold for detecting the differences in roadsurface height at two points is set to be larger than the firstthreshold for detecting the difference in road surface height at onepoint.

The position detector 42 can make each of values of road surface heightsat adjacent two points less likely to be detected as outlier points bymaking the second threshold TL2 for detecting differences in roadsurface height at two points larger than the first threshold TL1 fordetecting a difference in road surface height at one point as describedabove.

In this way, the road surface condition determiner 44 can appropriatelydetermine the condition of the road surface by making two outlier pointsless likely to be excluded than the case of one outlier point.

In addition, the corrector 43 can correct the road surface height at theposition at which the difference from an adjacent road surface height isequal to or larger than the predetermined threshold to a deformationlimit of the tire 15 (a limit value up to which a tire deformation modelis deformable). Furthermore, in this case, as the deformation limit ofthe tire 15, a gradient between adjacent road surface heights can beapplied.

In this way, it is possible to reduce measurement errors and improve adetection accuracy in detecting the condition of the road surface in acase where a road surface height at a measurement point exceeds thedeformation limit of the tire 15 due to woven wires or stones even whenthe road surface height at the measurement point is correct, forexample.

Here, the deformation limit of the tire 15 may be changed depending onthe type of the tire 15. For example, summer tires for summer requirehigh air pressures in general, while winter tires for winter relativelyrequire lower air pressures than those of the summer tires. For thisreason, the gradient as the deformation limit may be set lower forsummer tires for summer. Alternatively, the deformation limit of thetire 15 may be set depending on the aspect ratio of the tire 15.

In addition, when the gradient between adjacent road surface heights isapplied to the deformation limit of the tire 15, the gradient betweenroad surface heights may be calculate from distribution of weight of thevehicle V, for example, to set the deformation limit of the tire 15 tobe variable.

The deformation limit may be set to be variable depending on the weightdistribution of the vehicle V by, for example, setting the gradient asthe deformation limit for the tire 15 on the driver's seat side to belarger than the deformation limit for the tire 15 on the passenger'sseat side depending on the distribution of weight of the vehicle V. Inthis way, the ECU 4 can determine the condition of the road surface withhigh accuracy. By the way, it is possible to know the load applied toeach wheel (tire 15) by using the displacement (degree of depression) ofthe suspension (damper D) at a flat place and a result of measuring theroad surface, and it is also possible to set the deformation limit ofeach tire 15 based on this load.

In addition, for example, due to the air pressure of the tire 15, thehigher the air pressure is, the smaller the amount of change of the tire15 is. For this reason, the gradient as the deformation limit of thetire 15 can be set to be low. Note that the air pressure of the tire 15can be obtained any time if the vehicle is equipped with a tire pressuremonitoring system, TPMS.

In addition, when the vehicle V is being braked, the corrector 43 mayset a higher gradient as the deformation limit of the tires 15 for thewheels 16 of the front wheels than those of the rear wheels. Note thatin a case where the sensors 3 are provided only for the front wheels,this configuration can be applied as it is.

In addition, a difference may be set in gradient between the wheels 16that come on the inner wheel side when turning and the wheels 16 thatcome on the outer wheel side when turning, such that the value of thegradient as the deformation limit of the tire 15 on the outer wheel sideis higher than that on the inner wheel side. Note that thisconfiguration can be applied as it is during normal driving, and thevalue of the gradient can be set higher in the direction in whichcentrifugal force acts during turning a curve.

Second Embodiment

An ECU 4 according to a second embodiment includes: a road surfaceheight measurer 41 which measures road surface heights at three or morepoints along a vehicle-width direction in front of a tire mounted on awheel 16; a position detector 42 which detects a position at which adifference of the road surface height from an adjacent road surfaceheight is equal to or larger than a predetermined threshold among theroad surface heights at three or more points measured by the roadsurface height measurer 41; and a road surface condition determiner 44which excludes a value of the road surface height at the position atwhich the difference detected by the position detector 42 is equal to orlarger than the predetermined threshold, and determines a condition ofthe road surface based on the road surface heights at positions at eachof which the difference from an adjacent road surface height is smallerthan the predetermined threshold.

In this way, the ECU 4 according to the second embodiment detects theposition at which the difference from an adjacent road surface height isequal to or larger than the predetermined threshold, excludes a value ofthe road surface height at the position at which the detected differenceis equal to or larger than the predetermined threshold, and can thusdetermine the condition of the road surface based on the road surfaceheights at positions at each of which the difference from an adjacentroad surface height is smaller than the predetermined threshold.

As described above, the ECU 4 according to the second embodimentexcludes the value of the road surface height at a position at which thedifference detected by the position detector 42 is equal to or largerthan the predetermined threshold, and determines the condition of theroad surface based on the road surface heights at positions at each ofwhich the difference from an adjacent road surface height is smallerthan the predetermined threshold.

In this way, since the ECU 4 according to the second embodiment excludesa value of the road surface height of which the difference in roadsurface height is equal to or larger than the predetermined threshold,and can thus determine the condition of the road surface based on theroad surface heights of each of which the difference from an adjacentroad surface height is smaller than the predetermined threshold, and theaccuracy in detecting the condition of the road surface can thus beimproved.

In addition, the ECU 4 can determine a road surface height which isdesired to be deleted in consideration of the entire condition of theroad surface even when the road surface height is correct at ameasurement point due to a leaf or dust, and can thus reduce ameasurement error in the condition of the road surface. Since the ECU 4can reduce a measurement error in the condition of the road surface, itis possible to improve the accuracy in detecting the road surfacecondition. In this way, since the ECU 4 can improve the detectionaccuracy in detecting the condition of the road surface, it is possibleto prevent the ride comfort of an occupant in a car from deteriorating.

In particular, for the case where there is one point at which thedifference from an adjacent road surface height is equal to or largerthan the predetermined threshold and the case where there are two pointsat each of which the difference from an adjacent road surface height isequal to or larger than the predetermined threshold, the positiondetector 42 may be such that a larger second threshold for detecting thedifferences in road surface height at two points is set to be largerthan the first threshold for detecting the difference in road surfaceheight at one point.

As described above, the position detector 42 can make each of values ofroad surface heights at adjacent two points less likely to be detectedas an outlier point by making the second threshold TL2 for detectingdifferences in road surface height at two points larger than the firstthreshold TL1 for detecting a difference in road surface height at onepoint.

In this way, the road surface condition determiner 44 can appropriatelydetermine the condition of the road surface by making two outlier pointsless likely to be excluded than the case of one outlier point.

In addition, the road surface condition determiner 44 may be providedwith a noise removal function. For example, a predetermined outlierpoint may be removed by using information in the past and applying alow-pass filter which cuts off high-frequency components. In addition,an outlier point may be removed from continuity of measurement points byusing temporal (time-series) information in the past. In addition, theroad surface condition determiner 44 may be provided with a noiseremoval function including time-axis information based on speedinformation on the vehicle V.

What is claimed is:
 1. An active suspension device that is a controldevice for a variable damping force damper provided for damping arelative vibration between a vehicle body and a wheel, comprising: aroad surface height measurer which measures road surface heights atthree or more points along a vehicle-width direction in front of a tiremounted on the wheel; a position detector which detects a position atwhich a difference of the road surface height from an adjacent roadsurface height is equal to or larger than a predetermined thresholdamong the road surface heights at three or more points measured by theroad surface height measurer; and a corrector which corrects the roadsurface height at a position at which the difference detected by theposition detector is equal to or larger than the predetermined thresholdto a predetermined height.
 2. The active suspension device according toclaim 1, further comprising: a road surface condition determiner whichexcludes a value of the road surface height at the position at which thedifference detected by the position detector is equal to or larger thanthe predetermined threshold, and determines a condition of the roadsurface based on the road surface heights at positions at each of whichthe difference from an adjacent road surface height is smaller than thepredetermined threshold, wherein the corrector corrects the excludedvalue of the road surface height at the position at which the differenceis equal to or larger than the predetermined threshold based on the roadsurface heights at positions at each of which the difference from anadjacent road surface height is smaller than the predeterminedthreshold.
 3. The active suspension device according to claim 2, whereinfor a case where there is one point at which the difference from anadjacent road surface height is equal to or larger than thepredetermined threshold and a case where there are two points at each ofwhich the difference from an adjacent road surface height is equal to orlarger than the predetermined threshold, the position detector is suchthat a second threshold for detecting the differences in road surfaceheight at two points is larger than a first threshold for detecting thedifference in road surface height at one point.
 4. The active suspensiondevice according to claim 3, wherein the first threshold and the secondthreshold are variable.
 5. The active suspension device according toclaim 1, wherein the corrector corrects the road surface height at theposition at which the difference is equal to or larger than thepredetermined threshold to a limit value up to which the tire isdeformable.
 6. A control device for suspension comprising: a sensorwhich acquires information on the road surface heights at three or morepoints; and the active suspension device according to claim 1.